The present invention relates to an optical pickup device and particularly to an optical pickup device for optically performing at least either of recording and reproduction of information on an information recording medium such as optical disc.
FIG. 5 is a schematic configuration view of a conventional optical pickup device. The optical pickup device has a first light source 501, a second light source 502, an object lens 504, an optical monitor 505, and a light separation element 507. The light separation element 507 has a wavelength selection film 506.
The first light source 501 emits a first laser beam, and the second light source 502 emits a second laser beam different in wavelength from the first laser beam. The object lens 504 focuses the first laser beam and the second laser beam on a data recording surface of the optical disc 503. The optical monitor 505 detects light quantities of the first laser beam and the second laser beam. The wavelength selection film 506 reflects, in a direction of the object lens 504, the first laser beam emitted from the first light source 501 and allows the second laser beam emitted from the second light source 502 to pass therethrough, thereby making the beam incident on the object lens 504.
The beam from the first light source 501 and the beam from the second light source 502 are used for recording and reproduction on different types of optical discs. The optical monitor 505 detects the light beam emitted from the first light source 501 and having passed through the wavelength selection film 506 of the light separation element 507 and, on the other hand, detects the light beam emitted from the second light source 502 and reflected by the wavelength selection film 506 of the light separation element 507. Thus the light quantities of the laser beams that are necessary and indispensable for optically recording information on the optical disc 503 are detected and controlled.
In the optical pickup for recording, the light quantities of the outgoing laser beams are detected by the optical monitor 505 and are controlled to optimum recording powers. In a configuration of FIG. 5, the light quantities of the beams that can be used for the optical monitor 505 are restricted so as to be small because it is necessary to use most of the laser beams for the recording on the optical disc 503. More specifically, a transmittance through the wavelength selection film 506 in a path of the beam from the first light source 501 to the optical monitor 505 is set on the order of about 7%, and a reflectance through the wavelength selection film 506 in a path of the beam from the second light source 502 to the optical monitor 505 is also set on the order of about 7%.